Rotary machines such as gas turbines and steam turbines are a mechanism which rotates a rotating shaft. Some of such rotary machines having a rotating shaft are provided with a journal bearing (radial bearing) in order to receive the radial force and regulate the radial position of the rotating shaft (see Patent Literature 1).
In this connection, a journal bearing described in Patent Literature 1 is equipped with a mechanism, which supplies lubricating oil directly to the surface of a bearing pad by a direct lubrication method, in order to reduce the resistance between a rotor and a stator during rotation of the rotating shaft. Patent Literature 2 describes a mechanism for recovering lubricating oil mist which is provided with a bearing cover and a duct through which air inside a cavity formed by the bearing cover is discharged.
The direct lubrication method among bearing lubrication methods is a method of supplying lubricating oil directly to the surface of a bearing pad by means of an oil supply nozzle etc. and discharging the oil in the axial direction. The flow of lubricating oil around a rotating shaft in this method will be described using FIG. 13 and FIG. 14. FIG. 13 shows the flow of lubricating oil viewed from the axial direction of the rotating shaft. FIG. 14 shows the flow of lubricating oil viewed from the radial direction of the rotating shaft. The lubricating oil is supplied from a supply pump, which is disposed in a lubricating oil circulation mechanism (not shown) integrated in the rotary machine, through a pipe to a bearing mechanism.
As one example, FIG. 13 shows a cross-sectional view of a journal bearing from the axial direction of the rotating shaft. A bearing 150 has a carrier ring 161 having an upper carrier ring 161a and a lower carrier ring 161b, and an upper bearing pad 163, a lower bearing pad 164, and oil supply nozzles 166 disposed on the rotating shaft 20 side of the carrier ring 161. Lubricating oil L is supplied from an oil supply hole 167 provided in the lower carrier ring 161b of the bearing 150 to an oil passage 165, and after passing through the oil passage 165 provided inside the lower carrier ring 161b in the circumferential direction of the rotating shaft 20, the lubricating oil L is discharged from the oil supply nozzles 166 disposed in the lower bearing pad 164 to the surface of the rotating shaft 20. The plurality of oil supply nozzles 166 are disposed in the circumferential direction.
As shown in FIG. 14, the lubricating oil L, which is discharged from the oil supply nozzles 166 to the clearance between the surface of the rotating shaft 20 and the inner peripheral surface of the bearing 150, flows along the surface of the rotating shaft 20 to the upstream side and the downstream side in the axial direction. Both ends in the axial direction of the bearing 150 are covered with side plates 155, 156 over the entire circumference around the rotating shaft. The lubricating oil L is discharged from the clearance between the side plates 155, 156 and the surface of the rotating shaft 20 into the cavity inside the bearing cover where the bearing is disposed. The cavity is maintained at a reduced pressure by being suctioned from the lubricating oil circulation mechanism so that the oil mist of the lubricating oil etc. does not leak from the bearing cover to the outside. The lubricating oil L discharged from the bearing 150 is accumulated as oil drain DR at the bottom of the cavity, and is returned to the lubricating oil circulation mechanism to be used cyclically. The oil mist inside the cavity is suctioned and recovered by a suction mechanism which is installed inside the cavity and has a suction opening.